1. Field of the Invention
The invention relates to line transfer imagers, for television cameras, including a photosensitive zone formed from photosites, photodiodes or photo MOS, providing the light-detecting function.
During illumination, each photosite collects an electrical charge directly proportional to the received illumination. This function is obtained by adequate polarization of the photosites.
2. Description of the Prior Art
Traditionally the photosensitive zone is arranged as a matrix of m lines of p photosites. At the end of the integration period, the electrical charges stored on one line are read. For this, the line is selected by a line selecting logical shift register. This selection has the effect of causing the draining of the charges stored under the elementary image zones, or pixels, defined by the photodiodes, into the conducting columns connecting the elementary zones of like position. The charges thus deposited into the columns are transferred into a line memory during line suppression periods. This storage is temporary as these charges are very rapidly again transferred into a charge transfer output register. The line memory acts as a buffer between the pixel and the charge transfer register and provides an anti-glare control. As soon as the charges contained in the pixels have been transferred into the line memory, the line is disconnected and the integration of charges function is resumed. Each of the lines in the matrix is successively addressed in this way until the complete readout of the image. The French patent application No. 80 09112 in the name of the applicant gives a detailed description of an embodiment of such an imager.
In this system, the charges from the m photosites of like position i (i=1 to p) are all transferred into the same output register by means of a single conducting column connected to a single memory element. The memory elements form one or two line memories depending on whether or not there is a demultiplexing between the even points and the odd points of a single line. The addressing of the m lines of the matrix is carried out by one shift register for a readout of all the lines successively or by two shift registers one for the selection of even lines and the other for the selection of odd lines, for a readout per frame.
These structures are well suited to black and white single sensor cameras, but they do not allow the obtaining of an optimal image quality in single-sensor or three-sensor color cameras, in which the video signal results from the combination of several elementary signals corresponding to neighboring pixels possibly located in the same column.